Distance Visual Acuity

DIRECTIONS

• Use the Snellen Chart


• Position chart at a distance of 10 feet in front of client


• Chart needs to be positioned at client’s eye level


• Avoid placing the chart on a busy wall or on a glass window/door


• Do not stand next to the chart while assessing the client


• Practitioner should use a cheat sheet during assessment


• Test one eye, other eye, and both eyes


• Instruct the client to read the chart starting largest to smallest letters


• Practitioner should observe for sequencing errors, letters reversal, and reading right to left

RESULTS

• Normal = 20/20 ( the smallest line a person with normal acuity can read at a distance of 20%)


• Legal blind = 20/200


• VA driving = 20/40


• Acuity is represented as a fraction, with the distance as the numerator and the normal maximal legible viewing distance as the denominator


• Any mistake will be recorded as -1 (e.g. 20/40 -3 uncorrected)

CONTRAST SENSITIVITY

• The ability to detect features in different contrasts


• Measure ability to detect black car on white snowbank


• Client is seated during assessment